(1) Field of the Invention
This invention relates to an optical measuring system, and more particularly relates to the optical measuring system enabling to detect luminous intensity and chromaticity simultaneously.
(2) Description of the Prior Art
In present, various standard optical measuring systems are available for detecting LED chips or LED lamps. However, there has no suitable optical measuring system available for detecting LED light bars. Users have to adapt the optical measuring systems specified for detecting LED chips or LED lamps to detect LED light bars.
The optical measuring systems for detecting LED chips or LED lamps are designed to detect single isolated light source. In contrast, the LED light bar has a plurality of LED chips independently illuminate. Luminous intensity and chromaticity of each LED chip on the light bar should be detected. If the influence from the other LED chips on the light bar cannot be effectively removed, the detection cannot be correct.
FIG. 1 is a schematic view showing a typical optical measuring system detecting luminous intensity and chromaticity by using integrating sphere. As shown, light beams from the LED A to be detected project to an integrating sphere 14 through a tube 12. An optical sensor 16 is assembled on the integrating sphere 14 for detecting luminous intensity with unit Lumen. The integrating sphere 14 is connected to a fiber bundle 18 to transmit illumination to a spectrometry (not shown in this figure) for detecting chromaticity. It is noted that light beams generated by the LED A are uniformly diffuse reflected within the integrating sphere 14. Thus, the optical signals accessed in the optical sensor 16 and the fiber bundle 18 would not be affected by the intensity distribution of the light beams from the LED A. However, the optical measuring system has a poor efficiency about using the illumination of the LED A because only the light beams projecting to the optical sensor 16 and the fiber bundle 18 are collected.
FIG. 2 is a schematic view showing another typical optical measuring system. As shown, the optical measuring system has a lens 22, an aperture mirror 24, an optical receiver 28, and a view finder 26. The aperture mirror 24 is substantially located on a focal plane behind the lens 22. The light beams generated by the LED A are concentrated by the lens 22 to the aperture mirror 24. Part of the light beams arriving the aperture mirror 24 are reflected by the aperture mirror 24 to the view finder 26, and the other light beams penetrate the opening of the aperture mirror 24 and reach the optical receiver 28 behind the aperture mirror 24. The optical receiver 28 has a lens 28a and a light guide 28b. The light guide 28b is located behind the lens 28a. The light beams penetrating the aperture mirror 24 are concentrated by the lens 28a to the inlet of the light guide 28b, passing through the light guide 28, and projected to a spectrometry 29. The view finder 26 has a reflector 26a. The light beams projected to the view finder 26 are reflected by the reflector 26a toward the user's eyes for user to check whether the lens 22 is aligned to the LED A.
The view finder 26 is helpful for aligning the lens 22 to the LED A to be detected. The influence from the other LEDs B, C on the light bar can be reduced thereby. However, the settlement of the view finder 26 may increase the cost, size, and weight of the whole system. In addition, the optical measuring system uses the spectrometry 29 to detect absolute radiation spectrum of the LED A. The luminous intensity and chromaticity of the LED A computed by using absolute radiation spectrum detected usually takes a long calculation time and is not suitable for on-line high-speed measurement.
It is noted that the optical measuring systems provided in FIGS. 1 and 2 are specified for detecting single illuminating device. As the optical measuring systems are used to detect the LED A on the light bar 100, the unwanted influence of the other LED chips B, C on the light bar 100 or background illumination may result in measuring error.
Accordingly, it has become a major issue to reduce the influence of background illumination and to detect luminous intensity and chromaticity of the illuminating device rapidly and correctly.